The present invention relates generally to an aspirator. In particular, the present invention is directed toward an aspirator that improves mixing and gas contact, yet has reduced power requirements, by using a plurality of material-shedding, finned aspirator tubes to inject approximately 35% more air than the prior art design of U.S. Pat. No. 6,318,705 at the same rotational speed. Further, the aspirator of the present invention improves motor life by reducing the average current draw on the motor. The aspirator is useful in many applications, including sewage and wastewater treatment, oxygenation of fish ponds and aquaculture tanks, and any other gas-liquid mixing process such as, fermentation, aeration, hydrogenation, and oxidation. The aspirator is also useful in for providing vortex generation and air lift in a chamber used to separate oil from the sand and water solution in the production of synthetic crude oil from oil sands.
Prior art aspirators of this type are typically found in the field of wastewater treatment. Commonly assigned U.S. Pat. No. 5,599,452 to MacLaren et al. discloses a wastewater treatment method which uses such a conventional aspirator design.
Commonly assigned U.S. Pat. No. 6,318,705 to MacLaren discloses an aspirator design that is utilized to introduce air, oxygen, or other gases into a liquid. This design improved on the aspirator design of U.S. Pat. No. 5,599,452 with the ability to inject approximately 30% more air at 50% of the rotational speed. The aspirator included a 45 degree angle between the shaft and tubes to help shed debris that might otherwise collect on the aspirator and further included fins running along the entire length of the underside of the aspirator tubes to provide a larger profile for increased mixing. The present inventors consider this as the best prior art design for comparison purposes with the present invention, as detailed below.
U.S. Pat. No. 3,400,918 to MacLaren discloses a predecessor sewage aerator from the same inventor.
U.S. Pat. No. 4,844,843 to Rajendren and U.S. Pat. No. 5,160,667 to Gross disclose prior art liquid treatment aerators.
U.S. Pat. No. 3,776,531 to Ebner, et al. discloses an apparatus with separate propeller blades and aspirator tubes for dispersing and entraining a fluid, particularly a gas, in a liquid. This patent teaches that the aspirator tubes should be at an angle between 35 degrees and 75 degrees, when compared to the vertical axis of the shaft.
U.S. Pat. No. 5,318,360 to Langer, et al. discloses a gas dispersion stirrer comprising a rotatable shaft and at least one hollow, disk-shaped stirring/aspirating member. This patent teaches the inclusion of flow-inducing blades on both the top side and the bottom side of the disk-shaped member.
The Soviet Union patent SU 1,315,391 shows the utilization of swirlers 13 on the outer edges of the hollow vanes 5.
U.S. Pat. No. 3,779,531 to White shows some aeration tubes that are utilized at a downward angle compared to the vertical shaft.
The Japanese patent JP 63-028432 shows inclined aeration tubes in FIGS. 1 and 3.
U.S. Pat. No. 1,380,970 to Meridith-Jones shows the utilization of rods to break up liquid.
U.S. Pat. No. 1,124,855 to Callow, et al. shows angled aeration tubes 13 in FIG. 1.